KR20160078953A - Harq operation when tdd cell and fdd cell are included in carrier aggregation - Google Patents

Abstract

One disclosure of the present disclosure provides a method for performing HARQ operations at a user equipment (UE). The method includes the steps of: when one or more TDD based cells and one or more FDD based cells are set up according to a carrier aggregation (CA) and a specific TDD based cell is set as a primary cell of the carrier aggregation (CA) If the at least one FDD-based cell is set as a secondary cell of the FDD, the UE receives downlink data from each cell; Confirming a PUCCH format to be used by the UE to transmit HARQ ACK / NACK for the downlink data; And determining the number of transmission bits of the HARQ ACK / NACK if the UE is determined to use a particular PUCCH format for transmission of the HARQ ACK / NACK.

Description

(HARQ OPERATION WHEN TDD CELL AND FDD CELL ARE INCLUDED IN CARRIER AGGREGATION) in a situation where the TDD cell and the FDD cell are included in the carrier aggregation.

The present invention relates to mobile communications.

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an enhancement of Universal Mobile Telecommunications System (UMTS), is introduced as 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in the downlink and single carrier-frequency division multiple access (SC-FDMA) in the uplink.

Such LTE is divided into a frequency division duplex (FDD) scheme and a time division duplex (TDD) scheme.

As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) "Physical Channels and Modulation (Release 10) ", the physical channel in the LTE is a Physical Downlink (PDSCH) A Physical Uplink Control Channel (PDCCH), a Physical Uplink Shared Channel (PUSCH), and a Physical Uplink Control Channel (PUCCH).

Meanwhile, users are demanding faster data communication due to the spread of smart phones. At such a time when higher-speed data communication is required, it is inefficient for a mobile communication provider to provide only FDD-based services or FDD-based services only in terms of frequency usage. As a result, it may be desirable for the UE to be able to concurrently access both cells using FDD and cells using TDD. In order to realize this, there is a discussion about bundling FDD-based cells and TDD-based cells with carrier aggregation (CA) technology in the next generation mobile communication system.

However, when the FDD-based cell and the TDD-based cell are aggregated on the carrier, the HARQ operation of the UE becomes a problem.

Accordingly, the disclosure of the present specification aims at solving the above-mentioned problems.

In order to accomplish the above object, one aspect of the present disclosure provides a method for performing HARQ operations at a user equipment (UE). The method includes the steps of: when one or more TDD based cells and one or more FDD based cells are set up according to a carrier aggregation (CA) and a specific TDD based cell is set as a primary cell of the carrier aggregation (CA) If the at least one FDD-based cell is set as a secondary cell of the FDD, the UE receives downlink data from each cell; Confirming a Physical Uplink Control Channel (PUCCH) format to be used by the UE in order to transmit HARQ ACK / NACK for the downlink data; And determining the number of transmission bits of the HARQ ACK / NACK if the UE is determined to use a particular PUCCH format for transmission of the HARQ ACK / NACK. The maximum number of cells included in the carrier aggregation CA may be limited so that the number of transmission bits of the determined HARQ ACK / NACK does not exceed the maximum number of bits allowed in the PUCCH format.

If the PUCCH format to be used is PUCCH format 3 and the maximum allowable bit is 20 bits, the maximum number of cells included in the carrier aggregation (CA) may be limited.

If the PUCCH format to be used is PUCCH format 3, the maximum allowable bit is 20 bits, and the UL-DL setting of a specific TDD based cell corresponding to the primary cell corresponds to 2, 3, 4, or 5 , The maximum number of cells included in the carrier aggregation CA may be limited.

The method may further comprise receiving a setting for the PUCCH format to be used through the RRC signal.

The carrier aggregation (CA) may include TDD-based premier cells, FDD-based one or more secondary cells, and TDD-based one or more secondary cells.

In order to achieve the above object, one disclosure of the present disclosure also provides a method for receiving HARQ ACK / NACK in a TDD-based cell. The receiving method includes: setting a carrier aggregation (CA) with a TDD-based cell as a primary cell and a TDD-based cell and an FDD-based cell as a secondary cell; Wherein the TDD-based cell corresponding to the primary cell determines a Physical Uplink Control Channel (PUCCH) format to be used by the user equipment (UE); A TDD-based cell corresponding to the primary cell transmits downlink data to the UE; And receiving HARQ ACK / NACK for the downlink data from the UE. The maximum number of cells included in the carrier aggregation CA may be limited so that the number of received bits of the HARQ ACK / NACK does not exceed the maximum number of bits allowed in the PUCCH format.

According to the disclosure of the present specification, the problems of the above-described prior art are solved.

1 is a wireless communication system.
2 shows a structure of a radio frame according to FDD in 3GPP LTE.
3 shows a structure of a downlink radio frame according to TDD in 3GPP LTE.
4 is an exemplary diagram illustrating a resource grid for one uplink or downlink slot in 3GPP LTE.
5 shows a structure of a downlink sub-frame.
6 shows a structure of a UL subframe in 3GPP LTE.
7 shows PUCCH and PUSCH on the uplink subframe.
8 is a comparative example of a single carrier system and a carrier aggregation system.
9 illustrates cross-carrier scheduling in a carrier aggregation system.
10 is a diagram illustrating an operation of HARQ between a Node B and a UE.
FIGS. 11A and 11B show an example of grouping FDD-based cells and TDD-based cells, which are discussed in the next generation system, using carrier aggregation (CA) technology.
12 is a flow chart illustrating a scheme according to the second aspect of the present disclosure;
13 is a block diagram illustrating a wireless communication system in which the present disclosure is implemented.

Hereinafter, it is described that the present invention is applied based on 3rd Generation Partnership Project (3GPP) 3GPP long term evolution (LTE) or 3GPP LTE-A (LTE-Advanced). This is merely an example, and the present invention can be applied to various wireless communication systems. Hereinafter, LTE includes LTE and / or LTE-A.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "having ", etc. should not be construed as necessarily including the various elements or steps described in the specification, and some of the elements or portions thereof Or may further include additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

When an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may be present in between. On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the understanding of the present invention and should not be construed as limiting the scope of the present invention. The spirit of the present invention should be construed as extending to all modifications, equivalents, and alternatives in addition to the appended drawings.

The term base station, as used hereinafter, refers to a fixed station that typically communicates with a wireless device and includes an evolved-NodeB (eNodeB), an evolved-NodeB (eNB), a Base Transceiver System (BTS) Access Point).

Hereinafter, the term UE (User Equipment), which is used in the following description, may be fixed or mobile and may be a device, a wireless device, a terminal, a mobile station (MS), a user terminal (UT) , Subscriber station (SS), mobile terminal (MT), and the like.

1 is a wireless communication system.

1, the wireless communication system includes at least one base station (BS) 20. Each base station 20 provides a communication service to a specific geographical area (generally called a cell) 20a, 20b, 20c. A cell can again be divided into multiple regions (called sectors).

A UE typically belongs to one cell, and the cell to which the UE belongs is called a serving cell. A base station providing a communication service to a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication services to neighbor cells is called a neighbor BS. The serving cell and the neighboring cell are relatively determined based on the UE.

Hereinafter, the downlink refers to the communication from the base station 20 to the UE 10, and the uplink refers to the communication from the UE 10 to the base station 20. In the downlink, the transmitter may be part of the base station 20 and the receiver may be part of the UE 10. In the uplink, the transmitter may be part of the UE 10 and the receiver may be part of the base station 20.

On the other hand, the wireless communication system may be a multiple-input multiple-output (MIMO) system, a multiple-input single-output (MISO) system, a single-input single-output (SISO) It can be either. A MIMO system uses a plurality of transmit antennas and a plurality of receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas. Hereinafter, a transmit antenna means a physical or logical antenna used to transmit one signal or stream, and a receive antenna means a physical or logical antenna used to receive one signal or stream.

Meanwhile, the wireless communication system can be roughly divided into a frequency division duplex (FDD) system and a time division duplex (TDD) system. According to the FDD scheme, uplink transmission and downlink transmission occupy different frequency bands. According to the TDD scheme, uplink transmission and downlink transmission occupy the same frequency band and are performed at different times. The channel response of the TDD scheme is substantially reciprocal. This is because the downlink channel response and the uplink channel response are almost the same in a given frequency domain. Therefore, in the TDD-based wireless communication system, the downlink channel response has an advantage that it can be obtained from the uplink channel response. The TDD scheme can not simultaneously perform downlink transmission by the base station and uplink transmission by the UE because the uplink transmission and the downlink transmission are time-divisional in the entire frequency band. In a TDD system in which uplink transmission and downlink transmission are divided into subframe units, uplink transmission and downlink transmission are performed in different subframes.

Hereinafter, the LTE system will be described in more detail.

2 shows a structure of a radio frame according to FDD in 3GPP LTE.

The radio frame shown in FIG. 2 can refer to section 5 of 3GPP TS 36.211 V10.4.0 (2011-12) "Evolved Universal Terrestrial Radio Access (E-UTRA), Physical Channels and Modulation (Release 10)".

Referring to FIG. 2, a radio frame includes 10 subframes, and one subframe includes 2 slots. The slots in the radio frame are slot numbered from 0 to 19. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI is a scheduling unit for data transmission. For example, the length of one radio frame is 10 ms, the length of one subframe is 1 ms, and the length of one slot may be 0.5 ms.

The structure of the radio frame is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the like can be variously changed.

On the other hand, one slot may include a plurality of OFDM symbols. How many OFDM symbols are included in one slot may vary according to a cyclic prefix (CP).

3 shows a structure of a downlink radio frame according to TDD in 3GPP LTE.

This can be referred to Section 4 of 3GPP TS 36.211 V10.4.0 (2011-12) "Evolved Universal Terrestrial Radio Access (E-UTRA), Physical Channels and Modulation (Release 10) will be..

A radio frame includes 10 subframes indexed from 0 to 9. One subframe includes two consecutive slots. For example, the length of one subframe may be 1 ms and the length of one slot may be 0.5 ms.

One slot may comprise a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. OFDM symbols are used to represent one symbol period in the time domain since 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink (DL) It is not limited. For example, an OFDM symbol may be referred to as another name such as a single carrier-frequency division multiple access (SC-FDMA) symbol, a symbol period, or the like.

One slot may illustratively include 7 OFDM symbols, but the number of OFDM symbols included in one slot may be changed according to the length of the CP. One slot in a normal CP includes 7 OFDM symbols, and one slot in an extended CP includes 6 OFDM symbols.

A resource block (RB) is a resource allocation unit, and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain, and the resource block includes 12 subcarriers in the frequency domain, one resource block includes 7 × 12 resource elements (REs) .

A subframe having indexes # 1 and # 6 is called a special subframe and includes a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). DwPTS is used for initial cell search, synchronization, or channel estimation in the UE. UpPTS is used to match the channel estimation at the base station and the uplink transmission synchronization of the UE. The GP is a section for eliminating the interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

In TDD, DL (downlink) subframe and UL (Uplink) subframe coexist in one radio frame. Table 1 shows an example of the configuration of a radio frame.

[Table 1]

'D' denotes a DL sub-frame, 'U' denotes a UL sub-frame, and 'S' denotes a special sub-frame. Upon receiving the UL-DL setting from the base station, the UE can know which subframe is the DL subframe or the UL subframe according to the setting of the radio frame.

A DL (downlink) subframe is divided into a control region and a data region in a time domain. The control region includes up to three OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A PDCCH and another control channel are assigned to the control region, and a PDSCH is assigned to the data region.

4 is an exemplary diagram illustrating a resource grid for one uplink or downlink slot in 3GPP LTE.

Referring to FIG. 4, an uplink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and NRB resource blocks (RBs) in a frequency domain. For example, in the LTE system, the number of resource blocks (resource blocks RB), i.e. NRB, can be any of 6 to 110. [ The RB is also referred to as PRB (Physical Resource Block).

Here, one resource block (RB) exemplarily includes a 7 × 12 resource element (RE) including 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain. However, the number of sub- And the number of OFDM symbols are not limited thereto. The number of OFDM symbols or the number of subcarriers included in the resource block may be variously changed. That is, the number of OFDM symbols can be changed according to the length of the CP. Particularly, in the 3GPP LTE, seven OFDM symbols are included in one slot for a normal CP, and six OFDM symbols are included in one slot for an extended CP.

An OFDM symbol represents one symbol period and may be referred to as an SC-FDMA symbol, an OFDMA symbol, or a symbol interval depending on the system. The resource block includes a plurality of subcarriers in the frequency domain as a resource allocation unit. The number NUL of resource blocks included in the uplink slot is dependent on the uplink transmission bandwidth set in the cell. Each element on the resource grid is called a resource element (RE).

On the other hand, the number of subcarriers in one OFDM symbol can be selected from among 128, 256, 512, 1024, 1536 and 2048.

In the 3GPP LTE of FIG. 4, a resource grid for one uplink slot can be applied to a resource grid for a downlink slot.

5 shows a structure of a downlink sub-frame.

In FIG. 5, seven OFDM symbols are included in one slot, assuming a normal CP. However, the number of OFDM symbols included in one slot may be changed according to the length of a cyclic prefix (CP). That is, as described above, according to 3GPP TS 36.211 V10.4.0, one slot in a normal CP includes 7 OFDM symbols, and one slot in an extended CP includes 6 OFDM symbols.

A resource block (RB) is a resource allocation unit, and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block may include 7 x 12 resource elements (REs) have.

A DL (downlink) subframe is divided into a control region and a data region in a time domain. The control region includes up to three OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A Physical Downlink Control Channel (PDCCH) and another control channel are allocated to the control region, and a PDSCH is allocated to the data region.

In the 3GPP LTE, a physical channel includes a Physical Downlink Shared Channel (PDSCH), a Physical Uplink Shared Channel (PUSCH), a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator Channel (PCFICH) ARQ Indicator Channel) and PUCCH (Physical Uplink Control Channel).

The PCFICH transmitted in the first OFDM symbol of the subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (i.e., the size of the control region) used for transmission of the control channels in the subframe. The wireless device first receives the CFI on the PCFICH and then monitors the PDCCH.

Unlike PDCCH, PCFICH does not use blind decoding, but is transmitted through a fixed PCFICH resource of a subframe.

The PHICH carries an ACK (positive-acknowledgment) / NACK (negative-acknowledgment) signal for a hybrid automatic repeat request (UL HARQ). The ACK / NACK signal for UL (uplink) data on the PUSCH transmitted by the wireless device is transmitted on the PHICH.

A PBCH (Physical Broadcast Channel) is transmitted in four OFDM symbols preceding the second slot of the first subframe of the radio frame. The PBCH carries the system information necessary for the radio equipment to communicate with the base station, and the system information transmitted through the PBCH is called the master information block (MIB). In contrast, the system information transmitted on the PDSCH indicated by the PDCCH is called a system information block (SIB).

The PDCCH includes a resource allocation and transmission format of a downlink-shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information on a PCH, system information on a DL- Resource allocation of upper layer control messages such as responses, aggregation of transmit power control commands for individual UEs in any UE group, and activation of voice over internet protocol (VoIP). A plurality of PDCCHs may be transmitted in the control domain, and the UE may monitor a plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCH with the coding rate according to the state of the radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the possible PDCCH are determined according to the relationship between the number of CCEs and the coding rate provided by the CCEs.

The control information transmitted through the PDCCH is referred to as downlink control information (DCI). The DCI includes a set of transmission power control commands for individual UEs in any UE group, resource allocation (also referred to as DL grant) of the PDSCH, resource allocation of PUSCH (also referred to as UL grant) And / or Voice over Internet Protocol (VoIP).

The base station determines the PDCCH format according to the DCI to be sent to the UE, and attaches a CRC (cyclic redundancy check) to the control information. The CRC is masked with a unique radio network temporary identifier (RNTI) according to the owner or use of the PDCCH. If the PDCCH is for a particular UE, the unique identifier of the UE, e.g. C-RNTI (cell-RNTI), may be masked in the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, e.g., a paging-RNTI (P-RNTI), may be masked on the CRC. If the PDCCH is a PDCCH for a system information block (SIB), a system information identifier (SI-RNTI) may be masked in the CRC. A random access-RNTI (RA-RNTI) may be masked in the CRC to indicate a random access response that is a response to the transmission of the UE's random access preamble.

In 3GPP LTE, blind decoding is used for PDCCH detection. Blind decoding is a method for checking whether a corresponding PDCCH is a control channel by checking a CRC error by demodulating a desired identifier in a cyclic redundancy check (CRC) of a received PDCCH (referred to as a candidate PDCCH) . The base station determines the PDCCH format according to the DCI to be transmitted to the wireless device, attaches a CRC to the DCI, and masks a unique identifier (RNTI) to the CRC according to the owner or use of the PDCCH.

The control region in the subframe includes a plurality of control channel elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCH with the coding rate according to the state of the radio channel, and corresponds to a plurality of resource element groups (REGs). A REG includes a plurality of resource elements. The format of the PDCCH and the number of bits of the possible PDCCH are determined according to the relationship between the number of CCEs and the coding rate provided by the CCEs.

One REG includes four REs, and one CCE includes nine REGs. {1, 2, 4, 8} CCEs can be used to construct one PDCCH, and each element of {1, 2, 4, 8} is called a CCE aggregation level.

The number of CCEs used for transmission of the PDCCH is determined by the base station according to the channel state. For example, a UE having a good downlink channel state can use one CCE for PDCCH transmission. For a UE having a poor downlink channel state, eight CCEs can be used for PDCCH transmission.

A control channel composed of one or more CCEs performs REG interleaving and is mapped to a physical resource after a cyclic shift based on a cell ID is performed.

On the other hand, the UE can not know at which position in the control area its PDCCH is transmitted using any CCE aggregation level or DCI format. Since a plurality of PDCCHs can be transmitted in one subframe, the UE monitors a plurality of PDCCHs in each subframe. Here, monitoring refers to the UE attempting to decode the PDCCH according to the PDCCH format.

In 3GPP LTE, a search space is used to reduce the burden due to blind decoding. The search space is a monitoring set of the CCE for the PDCCH. The terminal monitors the PDCCH within the search space.

When the UE monitors the PDCCH based on the C-RNTI, the DCI format and the search space to be monitored are determined according to the transmission mode (TM) of the PDSCH. The following table shows an example of PDCCH monitoring in which C-RNTI is set.

[Table 2]

The use of the DCI format is divided into the following table.

[Table 3]

The uplink channel includes a PUSCH, a PUCCH, a sounding reference signal (SRS), and a physical random access channel (PRACH).

The uplink channel includes a PUSCH, a PUCCH, a sounding reference signal (SRS), and a physical random access channel (PRACH).

On the other hand, the PDCCH is monitored in a limited area called a control region in a subframe, and a CRS transmitted in the entire band is used for demodulating the PDCCH. As the types of control information are diversified and the amount of control information is increased, the flexibility of scheduling is degraded only by the existing PDCCH. Also, in order to reduce the burden due to CRS transmission, enhanced PDCCH (EPDCCH) is being introduced.

6 shows a structure of a UL subframe in 3GPP LTE.

Referring to FIG. 6, an uplink subframe may be divided into a control region and a data region in a frequency domain. A PUCCH (Physical Uplink Control Channel) for transmitting uplink control information is allocated to the control region. A data area is allocated a physical uplink shared channel (PUSCH) for transmitting data (in some cases, control information may be transmitted together).

The PUCCH for one UE is allocated as a resource block pair (RB pair) in a subframe. The resource blocks belonging to the resource block pair occupy different subcarriers in the first slot and the second slot. The frequency occupied by the resource blocks belonging to the resource block pair allocated to the PUCCH is changed based on the slot boundary. It is assumed that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary.

A frequency diversity gain can be obtained by transmitting uplink control information through different subcarriers according to time. and m is a position index indicating the logical frequency domain position of the resource block pair allocated to the PUCCH in the subframe.

The uplink control information transmitted on the PUCCH includes a hybrid automatic repeat request (HARQ) acknowledgment / non-acknowledgment (NACK), a channel quality indicator (CQI) indicating a downlink channel state, (scheduling request).

The PUSCH is mapped to a UL-SCH, which is a transport channel. The uplink data transmitted on the PUSCH may be a transport block that is a data block for UL-SCH transmitted during a transmission time interval (TTI). The transport block may be user information. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed transport block and control information for the UL-SCH.

7 shows PUCCH and PUSCH on the uplink subframe.

The PUCCH format will be described with reference to FIG.

Uplink control information (UCI) may be transmitted on the PUCCH. At this time, the PUCCH carries various kinds of control information according to a format. The UCI includes HARQ ACK / NACK, a Scheduling Request (SR), and channel status information (CSI) indicating a downlink channel status.

PUCCH format 1 carries a scheduling request (SR). At this time, an on-off keying (OOK) method can be applied. The PUCCH format 1a carries ACK / NACK (Acknowledgment / Non-Acknowledgment) modulated by a Binary Phase Shift Keying (BPSK) scheme for one codeword. The PUCCH format 1b carries an ACK / NACK modulated by a Quadrature Phase Shift Keying (QPSK) scheme for two codewords. PUCCH Format 2 carries a Channel Quality Indicator (CQI) modulated with a QPSK scheme. PUCCH formats 2a and 2b carry CQI and ACK / NACK.

Table 4 shows the PUCCH format.

[Table 4]

Each PUCCH format is mapped to the PUCCH area and transmitted. For example, the PUCCH format 2 / 2a / 2b is mapped and transmitted to a resource block (m = 0, 1 in FIG. 6) of the band edge allocated to the UE. The mixed PUCCH resource block (mapped PUCCH RB) may be mapped to a resource block allocated to the PUCCH format 2 / 2a / 2b and mapped to a resource block (e.g., m = 2) adjacent to the center of the band. The PUCCH format 1 / 1a / 1b to which the SR and the ACK / NACK are transmitted can be allocated to a resource block with m = 4 or m = 5. The number of resource blocks (N (2) RB) that can be used for the PUCCH format 2 / 2a / 2b to which the CQI is transmitted can be indicated to the UE through the broadcasted signal.

The CSI mentioned above is an index indicating the state of the DL channel, and may include at least one of a channel quality indicator (CQI) and a precoding matrix indicator (PMI). Also, a precoding type indicator (PTI), a rank indication (RI), and the like may be included.

The CQI provides information on the link adaptive parameters that the UE can support for a given time. The CQI may indicate a data rate that can be supported by the downlink channel in consideration of the characteristics of the terminal receiver and the signal to interference plus noise ratio (SINR). The base station can determine the modulation (QPSK, 16-QAM, 64-QAM, etc.) to be applied to the downlink channel and the coding rate using the CQI. The CQI can be generated in several ways. For example, a channel state can be directly quantized and fed back, a signal-to-interference plus noise ratio (SINR) can be calculated and fed back, and a MCS (Modulation Coding Scheme) have. When the CQI is generated based on the MCS, the MCS includes a modulation scheme, a coding scheme, and a coding rate according to the modulation scheme, the coding scheme, and the like.

The PMI provides information on the precoding matrix in the codebook-based precoding. PMI is associated with multiple input multiple output (MIMO). The feedback of PMI in MIMO is called closed loop MIMO (MIMO).

The RI is information on the number of layers recommended by the UE. That is, RI represents the number of independent streams used for spatial multiplexing. The RI is fed back only when the terminal operates in the MIMO mode using spatial multiplexing. RI is always associated with one or more CQI feedback. That is, the feedback CQI is calculated assuming a specific RI value. Since the rank of the channel generally changes slower than the CQI, the RI is fed back a number of times less than the CQI. The RI transmission period may be a multiple of the CQI / PMI transmission period. RI is given for the entire system band and frequency selective RI feedback is not supported.

As described above, the PUCCH is used only for transmission of the UCI. To this end, the PUCCH supports multiple formats. A PUCCH having a different number of bits per subframe may be used according to a modulation scheme depending on the PUCCH format.

Meanwhile, the illustrated PUSCH is mapped to a UL-SCH (Uplink Shared Channel), which is a transport channel. The uplink data transmitted on the PUSCH may be a transport block that is a data block for the UL-SCH transmitted during the TTI. The transport block may include user data. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed channel state information and a transport block for an uplink shared channel (UL-SCH). For example, channel state information (CSI) multiplexed on data may include CQI, PMI, RI, and the like. Alternatively, the uplink data may be composed of only channel state information. Periodic or aperiodic channel state information may be transmitted via the PUSCH.

The PUSCH is assigned by the UL grant on the PDCCH. Although not shown in the figure, the fourth OFDM symbol of each slot of the normal CP is used for transmission of DM RS (Demodulation Reference Signal) for PUSCH.

Now, the carrier aggregation system will be described.

8 is a comparative example of a single carrier system and a carrier aggregation system.

Referring to FIG. 8A, in a single carrier system, only one carrier is supported for uplink and downlink in a UE. The bandwidth of the carrier wave may vary, but one carrier is allocated to the UE. 8B, a plurality of element carriers (DL CC A to C, UL CC A to C) may be allocated to a UE in a carrier aggregation (CA) system. The component carrier (CC) means a carrier wave used in a carrier aggregation system and can be abbreviated as a carrier wave. For example, three 20 MHz element carriers may be allocated to allocate a bandwidth of 60 MHz to the UE.

A carrier aggregation system can be classified into a contiguous carrier aggregation system in which aggregated carriers are continuous and a non-contiguous carrier aggregation system in which aggregated carriers are separated from each other. Hereinafter, when it is simply referred to as a carrier aggregation system, it should be understood that this includes both continuous and discontinuous element carriers. The number of element carriers to be aggregated between the downlink and the uplink may be set differently. The case where the number of downlink CCs and the number of uplink CCs are the same is referred to as a symmetric aggregation, and the case where the number of downlink CCs is different is referred to as asymmetric aggregation.

When composing more than one element carrier, the element carrier can use the bandwidth used in the existing system for backward compatibility with the existing system. For example, in the 3GPP LTE system, a bandwidth of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz is supported. In the 3GPP LTE-A system, a bandwidth of 20 MHz or more can be configured using only the bandwidth of the 3GPP LTE system. Alternatively, a broadband may be configured by defining a new bandwidth without using the bandwidth of the existing system.

The system frequency band of a wireless communication system is divided into a plurality of carrier frequencies. Here, the carrier frequency means a center frequency of a cell. In the following, a cell may mean a downlink frequency resource and an uplink frequency resource. Or a cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. In general, in a case where a carrier aggregation (CA) is not considered, uplink and downlink frequency resources may always exist in one cell.

In order to transmit and receive packet data through a specific cell, the UE must first complete a configuration for a specific cell. Here, the 'configuration' means a state in which the reception of the system information necessary for data transmission / reception for the corresponding cell is completed. For example, the configuration may include common physical layer parameters required for data transmission / reception, or media access control (MAC) layer parameters, or a propagation process for receiving parameters required for a particular operation in the RRC layer . The set-up cell is in a state in which it can transmit and receive packets immediately when it receives only information that packet data can be transmitted.

The cell in the set completion state may be in an activated state or a deactivation state. Here, activation means that data transmission or reception is performed or is in a ready state. The UE may monitor or receive the active cell's control channel (PDCCH) and data channel (PDSCH) to ascertain the resource (which may be frequency, time, etc.) allocated to it.

Deactivation means that transmission or reception of traffic data is impossible and measurement or transmission / reception of minimum information is possible. The UE may receive System Information (SI) necessary for receiving a packet from the deactivation cell. On the other hand, the UE does not monitor or receive the control channel (PDCCH) and the data channel (PDSCH) of the deactivated cell in order to confirm the resource (which may be frequency, time, etc.) allocated to the UE.

A cell may be divided into a primary cell, a secondary cell, and a serving cell.

The primary cell refers to a cell operating at a primary frequency. The primary cell is a cell in which a UE performs an initial connection establishment procedure or connection re-establishment process with a base station, Cell.

A secondary cell is a cell operating at a secondary frequency, and once established, an RRC connection is established and used to provide additional radio resources.

The serving cell is configured as a primary cell if the carrier aggregation is not established or the UE is not capable of providing carrier aggregation. When carrier aggregation is set, the term serving cell indicates a cell set for the UE and may be composed of a plurality. One serving cell may be composed of one downlink component carrier or {pair of downlink component carrier, uplink component carrier}. The plurality of serving cells may consist of a primary cell and a set of one or more of all secondary cells.

As described above, unlike a single carrier system, the carrier aggregation system can support a plurality of element carriers (CC), i.e., a plurality of serving cells.

Such a carrier aggregation system may support cross-carrier scheduling. Cross-carrier scheduling may be performed by assigning a resource allocation of a PDSCH that is transmitted over a different element carrier over a PDCCH that is transmitted over a specific element carrier and / or a resource allocation of elements other than an element carrier that is basically linked with the particular element carrier A scheduling method that can allocate resources of a PUSCH transmitted through a carrier wave. That is, the PDCCH and the PDSCH can be transmitted through different downlink CCs, and the PUSCH can be transmitted through the uplink CC other than the uplink CC linked with the downlink CC to which the PDCCH including the UL grant is transmitted . Thus, in a system supporting cross-carrier scheduling, a carrier indicator is required to indicate to which DL CC / UL CC the PDSCH / PUSCH for providing control information is transmitted through the PDCCH. A field including such a carrier indicator is hereinafter referred to as a carrier indication field (CIF).

A carrier aggregation system that supports cross-carrier scheduling may include a carrier indication field (CIF) in a conventional downlink control information (DCI) format. For example, in the LTE-A system, the CIF is added to the existing DCI format (i.e., the DCI format used in LTE), so that 3 bits can be extended. The PDCCH structure can be divided into an existing coding method, Resource allocation method (i.e., CCE-based resource mapping), and the like can be reused.

9 illustrates cross-carrier scheduling in a carrier aggregation system.

Referring to FIG. 9, a base station can set up a PDCCH monitoring DL CC (monitoring CC) set. PDCCH Monitoring The DL CC aggregation is composed of some DL CCs among aggregated DL CCs. When cross-carrier scheduling is set, the UE performs PDCCH monitoring / decoding only on the DL CCs included in the PDCCH monitoring DL CC aggregation. In other words, the BS transmits the PDCCH for the PDSCH / PUSCH to be scheduled only through the DL CC included in the PDCCH monitoring DL CC set. PDCCH Monitoring The DL CC aggregation can be UE-specific, UE group-specific, or cell-specific.

FIG. 9 shows an example in which three DL CCs (DL CC A, DL CC B, and DL CC C) are aggregated and a DL CC A is set as a PDCCH monitoring DL CC. The UE can receive the DL grant for the PDSCH of DL CC A, DL CC B, and DL CC C through the PDCCH of DL CC A. The DCI transmitted through the PDCCH of the DL CC A may include the CIF to indicate which DC CC is for the DL CC.

We now describe HARQ in 3GPP LTE.

≪ HARQ (hybrid automatic repeat request) >

3GPP LTE uses synchronous HARQ in uplink transmission and asynchronous HARQ in downlink transmission. The synchronous HARQ means that the retransmission timing is fixed, and the retransmission timing of the asynchronous HARQ is not fixed. That is, the initial transmission and the retransmission are performed in the HARQ period of the synchronous HARQ.

10 is a diagram illustrating an operation of HARQ between a Node B and a UE.

First, a base station, i.e., the eNodeB 200, transmits scheduling information (hereinafter, referred to as scheduling information) through a Physical Downlink Control Channel (PDCCH) control channel in order to transmit data to the UE, i.e., the UE 100, .

The UE 100 monitors the control channel, i.e., the PDCCH, and confirms scheduling information to be transmitted to the UE.

When it is confirmed that the UE 100 has information about itself according to the confirmation of the scheduling information, the UE 100 transmits data from the eNodeB 200 through a physical shared channel (PSCH) at a time point associated with the PDCCH Data # 1 and data # 2).

When the UE 100 receives data, it attempts to decode the data. The UE transmits HARQ feedback to the eNodeB 200 according to the decoding result. That is, if the UE 100 succeeds in decoding, the UE 100 transmits an ACK signal, and if the UE 100 fails, transmits a NACK signal to the eNodeB 200 through the PUCCH or PUSCH.

Upon receiving the ACK signal, the eNodeB 200 detects that the data transmission to the UE has been successful and transmits the next data.

However, when the eNodeB 200 receives the NACK signal, it detects that the data transmission to the UE 100 has failed and retransmits the same data in the same format or new format at an appropriate time.

The UE 100 that has transmitted the NACK signal attempts to receive the retransmitted data.

When receiving the retransmitted data, the UE 100 combines the data stored in the buffer with the data stored in the buffer in a failed manner before attempting to decode the data again. If the UE 100 succeeds in decoding, the UE 100 transmits an ACK signal, NACK signal to the eNodeB 200 via the PUCCH or PUSCH. And repeats the process of transmitting a NACK signal and receiving a retransmission until decryption of the UE 100 data is successful.

≪ Carrier aggregation of FDD-based cells and TDD-based cells >

Meanwhile, users are demanding faster data communication due to the spread of smart phones. At such a time when higher-speed data communication is required, it is inefficient for a mobile communication provider to provide only FDD-based services or FDD-based services only in terms of frequency usage. As a result, it may be desirable for the UE to be able to concurrently access both cells using FDD and cells using TDD. In order to realize this, there is a discussion about bundling FDD-based cells and TDD-based cells with carrier aggregation (CA) technology in the next generation mobile communication system.

FIGS. 11A and 11B show an example of grouping FDD-based cells and TDD-based cells, which are discussed in the next generation system, using carrier aggregation (CA) technology.

First, as shown in FIG. 11A, the base station 200 can be improved so as to provide FDD-based cells and TDD-based cells, respectively. In addition, the base station 200 may bundle the FDD-based cells and the TDD-based cells using carrier aggregation (CA) technology. Therefore, the UE 100 can use both the FDD-based cell and the TDD-based cell according to the carrier aggregation (CA) technique.

On the other hand, as shown in FIG. 11B, a small base station having a small cell coverage radius may be disposed in the coverage within the base station 200. [ Since the coverage of the base station 200 is larger than that of the small base station, the base station 200 may be called a macro base station. The cell provided by the macro base station may be referred to as a macro cell. The cell provided by the small base station may be referred to as a small cell. The macro base station may provide an FDD based cell as shown, for example, and the small base station may provide a TDD based cell as shown. The FDD-based cells of the macro base station and the TDD-based cells of the small base station may be bundled using a carrier aggregation (CA) technique.

However, when the FDD-based cell and the TDD-based cell are aggregated on the carrier as described above, the HARQ operation of the UE 100 becomes a problem.

≪ Disclosure of the present specification &

Accordingly, the present disclosure aims at suggesting measures for allowing UE 100 to perform HARQ operations normally when FDD-based cells and TDD-based cells are aggregated on a carrier.

I. First Publication of the Specification

First, in the 3GPP Release 11, the UE can transmit and receive data from a plurality of cells having the same frame structure type (e.g., FDD or TDD). However, as described above, in the next system, it is possible to consider an environment for transmitting / receiving data / control information from one terminal to a plurality of cells using different frame structure types (FDD and TDD) for flexible management and operation of frequency bands have. That is, the FDD-based cell and the TDD-based cell can be aggregated and provided to the UE. Hereinafter, the FDD-based cell and the TDD-based cell are collectively called a 'TDD-FDD CA'.

In the TDD cell in the TDD-FDD CA, the uplink (UL) and the downlink (DL) exist in a time-varying manner according to the setting of the UL-DL shown in Table 1, (DL) is always present. Assume that the FDD cell follows the existing TDD timing. In the FDD cell, there exist subframes for which the scheduling method is not set. For example, when the TDD UL-DL setting is 1 and the FDD cell also follows the TDD UL-DL setting 1, in the case of downlink (DL) HARQ-ACK, For the subframe, there is no scheduling method or a method of transmitting HARQ-ACK even though a downlink (DL) exists in the FDD. If the scheduling is not performed on the downlink (DL) subframe, the maximum number of aggregable cells is limited to two when the reference UL-DL setting is 5 as in the conventional TDD scheme, You may also choose to allow up to five.

According to an embodiment of the present invention, additional timing may be designated according to various schemes in order to increase the flexibility of resource operation, that is, to utilize the DL sub-frame of the FDD cell. For example, according to a first scheme, the UE may send a HARQ-ACK in the fastest available UL subframe after 4ms after receiving the PDSCH. Alternatively, according to the second scheme, additional HARQ-ACK timing may be distributed among a plurality of subframes in order to prevent performance deterioration that may occur when HARQ-ACK bits are included in a specific subframe during HARQ-ACK transmission. According to the third scheme, it is possible to prevent the HARQ-ACK transmission time for one PDSCH from exceeding the HARQ-ACK transmission time for the PDSCH corresponding to a time point earlier than the corresponding PDSCH. The following table shows an example of HARQ transmission timing.

[Table 5]

In the above table, square brackets [] are the numbers of newly added PDSCH receiving subframe K according to each scheme.

In the above table, square brackets [] are the numbers of newly added PDSCH receiving subframe K according to each scheme.

Using the additional FDD downlink (DL) subframe according to the first scheme and the second scheme out of the above schemes, the bits of the HARQ ACK / NACK that can be transmitted at one time on the uplink subframe n may be exceeded have.

Therefore, it is necessary to limit the number of collectable ones. This limitation can be applied to a case where a UE performing a TDD-FDD CA follows a TDD timing in transmitting an HARQ-ACK. This limitation also applies when the TDD-based cell is the primary cell of the carrier aggregation and the FDD-based cell is the secondary cell of the carrier aggregation. The downlink (DL) HARQ-ACK timing of the FDD-based cell for the subframe corresponding to the downlink (DL) in the TDD-based cell can basically follow the UL-DL setting of the TDD-based primary cell . Meanwhile, a subframe not corresponding to the set TDD UL-DL among the DL subframes of the FDD cell may be referred to as a remaining downlink (DL) subframe.

Hereinafter, a method for limiting the maximum number of aggregable cells will be described.

II. The second aspect of the present disclosure is that the maximum number of aggregable cells

The maximum number of cells to be subjected to the carrier aggregation (CA) depends on whether or not a plurality of HARQ-ACKs can be transmitted. For example, when PUCCH format 3 is supported, HARQ-ACK can be allowed up to 20 bits, and the maximum number of cells to be subjected to carrier aggregation is set based on a criterion in which the number of HARQ-ACK bits does not exceed 20 bits .

The following is a specific example of a method of setting the maximum number of aggregable cells according to the TDD UL-DL setting. The TDD UL-DL setting may be a setting corresponding to the TDD cell in the TDD-FDD CA or an UL-DL setting in which the FDD cell refers to the downlink (DL) HARQ-ACK transmission timing. In the embodiment of the present invention, the maximum number of cells that can be aggregated with respect to the TDD cell constituting the carrier aggregation (CA) has been described. However, the method of setting the number of the FDD cells constituting the carrier aggregation (CA) It is obvious that it can be done.

(1) TDD UL-DL setting 0

In this case, the maximum value of the number (M) of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 1. According to the UL-DL setting, one radio frame includes six uplinks (UL), and thus the number of remaining downlink (DL) subframes of the FDD cell is six. Therefore, the maximum number of aggregable cells can be determined to be 5 regardless of the HARQ-ACK timing setting of the remaining DL subframe.

(2) TDD UL-DL setting 1

In this case, the maximum value of the number M of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 2. According to the UL-DL setting, one radio frame includes four uplinks (UL), and thus the number of remaining DL subframes of the FDD cell is four. The maximum number of aggregable cells is determined to be 5 regardless of the HARQ-ACK timing setting of the remaining DL subframe.

(3) TDD UL-DL setting 2

In this case, the maximum value of the number M of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 4. According to the UL-DL setting, one radio frame includes two uplinks (UL), and thus the number of remaining downlink (DL) subframes of the FDD cell is also two. In the UL-DL setting, the number of HARQ-ACK bits (including the use of spatial bundling) is at most 20 bits based on the aggregation of five cells when FDD residual DL subframe is not used, Therefore, when using the residual downlink (DL) subframe of the FDD, the maximum number of aggregable cells should be set to less than 5. In the UL-DL setup, since the downlink-uplink switching period is 5 ms and the number of uplink (UL) subframes per 5 ms is one, the first scheme, the second scheme, and the third scheme described with reference to Table 5 There is no difference in the method. Therefore, when using the remaining downlink (DL) subframe of the FDD, the maximum number of aggregable cells can be determined to be 4. More specifically, when the number of information bits for PUCCH format 3 is extended to 22 bits, the maximum number of aggregable cells can be extended to 5 when the number of FDD cells constituting CA is 1. FIG.

(4) TDD UL-DL setting 3

In this case, the maximum value of the number (M) of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 3. According to the UL-DL setting, one radio frame may include three uplinks (UL), and thus the number of remaining DL subframes of the FDD cell is three. If the residual DL subframe of the FDD is utilized according to the second scheme described with reference to Table 5 above, the maximum number of aggregable cells can be set to 5. [ However, when the residual DL subframe of the FDD is utilized in the first scheme described with reference to Table 5, the maximum number of aggregable cells can be set according to the following example. Here, the first scheme described above is applicable to the third scheme because the third scheme and the HARQ timing are the same.

According to a first example, the maximum number of aggregable cells for convenience is fixed to four. In this case, it is possible to limit the information bits for PUCCH format 3 to a total of 22 bits. When the number of information bits for PUCCH format 3 is limited to 21 bits in total, the maximum number of aggregable cells is fixed to 3.

According to the second example, the maximum number of acceptable aggregable cells is determined according to the combination of the number of TDD cells and the number of FDD cells included in the carrier aggregation CA. Up to two TDD cells, the maximum number of aggregable cells is set to four, and other cells are allowed up to five. In this second example, the information bits for PUCCH format 3 may be applied to a total of 22 bits. When the number of information bits for PUCCH format 3 is limited to 21 bits in total, the maximum number of aggregable cells is set to three when one TDD cell is used, and the maximum number of aggregable cells is four when two or three TDD cells are used , Otherwise allow up to 5 cells.

According to the third example, when the number of TDD cells included in the carrier aggregation (CA) is two or more, considering the different TDD UL-DL setting among the TDD cells, the M value for the TDD cell may be assumed to be four. Here, the case where the reference UL-DL setting is 5 between the TDD cells can be excluded. According to the third example, the maximum number of acceptable aggregable cells can be determined according to the combination of the number of TDD cells and the number of FDD cells included in the carrier aggregation CA. If there are four TDD cells, the maximum number of aggregable cells is determined to be 5, and otherwise, up to four cells can be allowed. In this second example, the information bits for PUCCH format 3 may be applied to a total of 22 bits. When the number of information bits for PUCCH Format 3 is limited to 21 bits in total, the maximum number of aggregable cells is set to 3 when one TTDD cell is used, and up to 4 cells are allowed for other TTDD cells.

(5) TDD UL-DL setting 4

In this case, the maximum value of the number M of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 4. According to the UL-DL setting, one radio frame includes two uplinks (UL), and therefore, the number of remaining downlink (DL) subframes of the FDD cell is also two. If the remaining DL subframe of the FDD is used according to the second scheme described with reference to Table 5 above, the maximum number of aggregable cells can be set to 4. When the number of information bits for the PUCCH format 3 is extended to a total of 22 bits in the second scheme, when the number of TDD cells constituting the carrier aggregation (CA) is 1, the maximum number of aggregable cells is set to 5 It can also be extended. However, when the residual DL subframe of the FDD is utilized in the first scheme described with reference to Table 5, the maximum number of aggregable cells can be set according to the following example. Here, the first scheme described above is applicable to the third scheme because the third scheme and the HARQ timing are the same.

According to a first example, the maximum number of collectable cells for convenience can be fixed at 3.

According to the second example, the maximum number of acceptable aggregable cells can be determined according to the combination of the number of TDD cells and the number of FDD cells included in the carrier aggregation CA. The maximum number of cells that can be aggregated up to one TDD cell is set to 3, and up to four cells are allowed.

According to a third example: the maximum number of aggregable cells can be fixed at 4. [ In this case, the information bits for PUCCH format 3 can be limited to 22 bits in total. In the case of four aggregable cells, the number of HARQ-ACK bits is 22 bits at most, and only HARQ-ACKs can be transmitted in a subframe in which no SR is set. In this example, it can be assumed that some HARQ-ACKs are not transmitted for the subframe in which the SR is set, and it can be assumed that the PDSCH is not scheduled in the corresponding downlink (DL) subframe. The DL subframe may be limited to all or part of the remaining DL subframes of the FDD cell. The scheduling restriction according to the setup sub-frame of the SR can be applied to a carrier aggregation (CA) including one TDD cell and three FDD cells.

(6) TDD UL-DL setting 5

In this case, the maximum value of the number M of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 5 or more. According to the UL-DL setting, one radio frame may include one uplink (UL), so that the number of remaining DL subframes of the FDD cell is also one. The maximum number of aggregable cells can be set to 2 irrespective of the setting of the HARQ-ACK time of the remaining DL subframe. Since the UL subframe is one, the timing of setting the remaining DL subframes can be regarded as one. In this case, the number of HARQ-ACK bits per cell (if necessary, spatial bundling , And the total number of bits of HARQ-ACK is set to 20 bits when two cells are aggregated.

(7) TDD UL-DL setting 6

In this case, the maximum value of the number (M) of downlink (DL) subframes corresponding to a single uplink (UL) subframe can be expressed as 1. According to the UL-DL setting, one radio frame may include five uplinks (UL), so that the number of remaining DL subframes of the FDD cell is also five. The maximum number of aggregable cells is set to 5 regardless of the HARQ-ACK timing setting of the remaining DL subframe.

The following additional example can be considered when setting or limiting the maximum number of aggregable cells in the aggregation of TDD and FDD cells.

According to the first example, when it is assumed that the TDD cell and the FDD cell are carrier aggregated, the maximum number of aggregated cells can be limited to two regardless of the TDD UL-DL setting. In the above, the TDD-FDD CA may follow the TDD HARQ timing.

According to the second example, when the TDD cell and the FDD cell are aggregated on the carrier, the maximum number of aggregated cells is limited to two for the TDD UL-DL setting in which the maximum number of aggregated cells can not be set to five. At this time, the TDD-FDD CA can be limited to the case of following the TDD HARQ timing. More specifically, the TDD UL-DL setting can be limited to 2, 3, 4, and 5. If the remaining DL subframe of the FDD cell is supported by the second scheme described with reference to Table 5 in the case of TDD UL-DL setting 3, UL-DL setting that does not support the five cells Can be excluded. According to this, the maximum value of M including the remaining DL sub-frames of the FDD is 4 or less, but the maximum number of aggregated cells is allowed to be 5.

The contents described so far will be summarized below with reference to FIG.

12 is a flow chart illustrating a scheme according to the second aspect of the present disclosure;

Referring to FIG. 12, the TDD-based cell is the primary cell of the carrier aggregation and the FDD-based cell is the secondary cell of the carrier aggregation.

First, a TDD-based cell corresponding to a primary cell determines a PUCCH format of the UE 100, and transmits a PUCCH configuration including information on the determined PUCCH format to the UE 100 via an RRC signal.

Then, a TDD-based cell corresponding to the primary cell determines the maximum number of cells capable of aggregating carriers. For example, if the PUCCH format 3 is determined as the PUCCH format of the UE 100 in the above determination, the maximum number of cells may be determined so that the HARQ ACK / NACK to be transmitted by the UE does not exceed 20 bits.

Then, the TDD-based cell delivers an RRC reconfiguration message to add a secondary cell in a range not exceeding the maximum number of the determined cells. Here, the added secondary cell may include an FDD-based cell.

The UE 100 transmits an RRC reconfiguration completion message to the TDD-based cell in response to the RRC reconfiguration message.

Next, the TDD-based cell transmits an activation message to the UE 100 to activate the secondary cell.

Each cell transmits PDCCH including scheduling information, and then transmits a PDSCH including downlink data to the UE 100, respectively.

When the UE 100 receives the downlink data, it must transmit an HARQ-ACK / NACK for each downlink data.

At this time, if the PUCCH format is PUCCH format 3, the UE 100 determines the number of HARQ-ACK / NACK bits to be transmitted in the uplink subframe n. If the DL-reference UL-DL setting of the TDD-based cell corresponds to 2, 3, 4, or 5, the UE 100 transmits the HARQ-ACK / It can be assumed that the number of the carrier-accumulated cells is limited so that the number of bits does not exceed 20.

III. A plan for collecting up to 5 cells

In determining the bits of the HARQ-ACK / NACK to be transmitted, it is possible to use a method of limiting the number of cells to be used for the carrier aggregation (CA) by using all available subframes for each cell as described above The maximum number of cells to be subjected to the carrier aggregation (CA) is fixed to 5 and only a part of the remaining DL subframes of the FDD cell can be utilized according to the limit to be transmitted through the PUCCH resource. Alternatively, it is also possible to consider a method of transmitting a signal after reducing the number of bits through HARQ-ACK through bundling or the like.

(1) Use of a downlink (DL) subframe of an FDD cell aligned with an uplink (UL) subframe of a TDD cell

For the TDD-FDD carrier aggregation (CA), when the maximum number of aggregable cells is maintained at 5, the remaining DL subframes of the FDD cell need to be limited to all or part of the scheduling. The following is a more specific example of the usage setting and selection method of the remaining downlink (DL) subframe of the FDD.

As a first example, when following the TDD HARQ timing in the TDD-FDD carrier aggregation (CA), the number of downlink (DL) subframes connected to each uplink (UL) And sets whether all or part of the DL subframe is used. Here, a DL subframe connected to an uplink (UL) subframe may be a downlink (DL) subframe corresponding to a corresponding HARQ-ACK when transmitting a plurality of HARQ-ACKs in an uplink (UL) ) ≪ / RTI > subframe. For example, when the TDD cell and the FDD cell set in the UL-DL setting 3 are bundled by the carrier aggregation and follow the TDD downlink (DL) HARQ timing, in the case of the second scheme described with reference to Table 5, The maximum value (hereinafter referred to as M) of the number of downlink (DL) subframes connected to a single uplink (UL) subframe does not exceed four. In the case of the first scheme and the third scheme described with reference to Table 5 above, the maximum value of M may be 6, but according to the present method, one remaining downlink (DL) subframe among the three remaining downlink ) ≪ / RTI > subframe, the maximum value of M can be set to four. Here, when the number of HARQ-ACK bits exceeds 20, all or some of the remaining DL subframes of the FDD cell may not be used.

As a second example, the use of all or part of the remaining DL subframes of the FDD cell is set according to the number of cells constituting the carrier aggregation (CA) in the TDD-FDD carrier aggregation (CA). More specifically, in the case of UL-DL setting 2, all remaining downlink (DL) subframes of the FDD cell are allowed to be used up to four cells constituting the carrier aggregation (CA) I never do that. In the case of the first scheme and the third scheme described with reference to Table 5 in the UL-DL setting 3, up to four cells constituting the carrier aggregation CA are allocated to all the remaining DL sub- Allows use of frames, but does not allow for 5 cells. In the case of the first scheme and the third scheme described with reference to Table 5 in the UL-DL setting 4, up to three cells constituting the carrier aggregation CA are allocated to all the remaining DL sub- Allows use of frames, and does not allow for 4 or 5 cells s. In the case of the second scheme described with reference to Table 5 in the UL-DL setting 4, the use of all remaining DL sub-frames of the FDD cell is permitted up to four cells constituting the carrier aggregation (CA) , But not for 5 cells. The above description may be expressed as not using all or some of the remaining DL subframes of the FDD cell when the number of HARQ-ACK bits exceeds 20. [

Here, the use of all or some of the remaining DL subframes of the FDD cell may be set in an upper layer. At this time, the setting scheme may be designated for each DL sub-frame.

On the other hand, as a more specific example, it may be considered to (re) set the HARQ timing so that M> 4 does not occur for TDD UL-DL settings 2, 3 and 4. More specifically, with respect to the TDD UL-DL setting 3, the HARQ timing may not be the second scheme described with reference to Table 5 above.

As a modification of the first example, the UL-DL setting may follow the timing of the existing TDD primary cell. The TDD primary cell timing may be set via the SIB, or may be the actual reference timing in use in the primary cell. For example, when the TDD primary cell is operating in the UL-DL setting 4, it can be considered that the HARQ timing of the FDD secondary cell in the cell and the carrier aggregation (CA) conforms to the UL-DL setting 4. At this time, additional timing can be assigned as long as M < = 4. For example, when the UL-DL setting 4 is used, in the first scheme described with reference to Table 5, if the HARQ ACK / NACK transmission subframe n is 2, the downlink subframe K is allowed to be either 10 or 9 have.

As another modification of the first example, it is assumed that one of the values of the TDD UL-DL setting 0-6 is followed for the corresponding UL-DL setting. More specifically, if the FDD cell is a secondary cell, the downlink (DL) HARQ timing of the FDD cell may be set to the UL-DL setting 5 or the UL-DL setting 2 may be set to the setting 2 timing.

At this time, it may be considered to determine the HARQ timing on the basis of another setting depending on the number of cells constituting the carrier aggregation CA. For example, the timing according to setting 5 is used when the number of cells to be subjected to total carrier aggregation (CA) is two, and the timing according to setting 2 is used when the number of cells to be subjected to total carrier aggregation (CA) Can be considered. Here, in the case of using the timing according to setting 2, it can be applied to a case where the TDD cell is the primary cell and the timing of the TDD cell is the setting 2. Here, when the TDD cell is the primary cell, the timing of the primary cell may be set via the SIB or the actual reference timing in use in the primary cell.

At this time, the timing according to setting 2 or the timing according to setting 5 may be the existing timing or the timing shown in Table 5 above.

(2) Configuration scheme of HARQ-ACK / NACK bit for transmission in PUCCH format 1b with channel selection

When the number of cells constituting the TDD-FDD carrier aggregation CA is two, it may be considered to use the PUCCH format 1b capable of channel selection in transmitting a plurality of HARQ-ACK / NACKs. However, the PUCCH format 1b method capable of selecting a channel in the existing 3GPP Rel-11 system has a problem in that when the maximum number of DL subframes (denoted by M) connected to an uplink (UL) subframe to transmit the PUCCH is four It is necessary to support a case where the value of M is 5 (and 6) when using additional bits of the FDD cell in the TDD-FDD carrier aggregation (CA). This will be described below.

1) New table design method

The table design of the PUCCH format 1b capable of channel selection for the case of M = 5 or 6 can consider a DAI-based scheme such as M = 3 or 4. If the TDD cell is the primary cell, the HARQ-ACK can be transmitted through the PUCCH format 1b in which the value of M (hereinafter referred to as M_P cell) is maximum 4 when the channel is selectable. Based cell is a secondary cell, a case where the value of the M_P cell and the value of the M_S cell (M of the S cell) are different may be considered. For example, the case where the M_P cell is 4 and the M_S cell is 5 can be considered. Alternatively, it is also possible to select a table of the PUCCH format 1b that can select a channel by setting the Max value of the M_P cell and the M_S cell as the final M value. For example, the case of M_P cell = M_S cell = 5 can be considered. The following are more specific examples.

As a first example, the value of the M_P cell and the value of the M_S cell are made independent of the TDD-FDD carrier aggregation (CA), and the HARQ-ACK bit for the PUCCH format 1b capable of channel selection is configured using the value of the M_P cell.

As a second example, an HARQ-ACK bit for a PUCCH format 1b capable of channel selection is configured using the value of the M_P cell and the maximum value of the M_S cells only for the TDD-FDD carrier aggregation (CA).

As a third example, if the value of the M_S cell is 5 in the TDD-FDD carrier aggregation (CA), apply the scheme of the first example above. If the value of the M_S cell is 4 or less, the second example above is applied .

As a fourth method, in the TDD-FDD carrier aggregation (CA), the UE receives the value of the M_S cell for the secondary cell corresponding to the FDD-based cell through the upper layer signal. In this case, scheduling restrictions and the like may be additionally considered.

In the above example, HARQ-ACK transmission may be performed for each cell, and considering the continuous ACK counter, it may be considered to reduce the number of HARQ-ACK bits to 2 bits per cell. Here, the 2 bits are the converted HARQ-ACK (Ack, Ack), (Ack, Nack / DTX), (Nack / DTX, Ack), (Nack / DTX, Nack / DTX) . &Lt; / RTI &gt; Thereafter, PUCCH resources and transmission symbols can be set according to the scheme shown in the following table by inputting 4-bit converted HARQ-ACK for two cells. The table below shows the transmission of HARQ-ACK multiplexing for A = 4.

[Table 6]

The HARQ-ACK (0) and the HARQ-ACK (1) are the converted HARQ-ACK for the primary cell and the HARQ-ACK (2) and the HARQ-ACK (3) .

The following is a specific example of the HARQ-ACK compression conversion method for M = 5. In a concrete example, HARQ-ACK (k) is a HARQ-ACK corresponding to a subframe including a PDCCH / EPDCCH indicating a k-th scheduled PDSCH transmission or a semi-persistent scheduling release, k-1) mod 4 +1).

As a first example, it is assumed that a DL subframe (hereinafter referred to as a residual DL subframe) of an FDD cell associated with a TDD uplink (UL) subframe corresponds to HARQ-ACK (4) . And the residual DL sub-frame is intended to increase the peak data rate. The HARQ-ACK conversion method for this case can be followed by the following table. The following table shows an example of the HARQ-ACK compression conversion method for M = 5.

[Table 7]

As a second example, we design a table with a higher data rate for M = 5. The following table is an example of a HARQ-ACK compression conversion method for M = 5 as a specific example.

[Table 8]

In the Converted HARQ-ACK state (ACK, ACK) may be set to (NACK / DTX, NACK / DTX) and vice versa. And (ACK, NACK / DTX) may be set to (NACK / DTX, ACK) and vice versa. In the case of the secondary cell, (NACK / NACK / DTX) and (DTX, NACK / DTX) may be considered in the converted HARQ-ACK state (NACK / DTX, NACK / DTX).

As a third example, a table is designed with a low data rate for M = 5. The following table is an example of a HARQ-ACK compression conversion method for M = 5 as a specific example.

[Table 9]

As a fourth example, a table is designed with a low data rate for M = 5. The following table shows an example of HARQ-ACK compression conversion method for M = 5.

[Table 10]

As a fifth example, a table is designed by appropriately distributing data rates for M = 5. The following table is an example of a HARQ-ACK compression conversion method for M = 5.

[Table 11]

As a sixth example, a table is designed for M = 5. At this time, the number of overlapping HARQ-ACK states is increased. The following table shows an example of HARQ-ACK compression conversion method for M = 5.

[Table 12]

S1 and S2 above may be set to NACK / DTX, DTX, or any, respectively.

In the Converted HARQ-ACK state (ACK, ACK) may be set to (NACK / DTX, ACK) and vice versa. In some cases, the PUCCH resource mapping and the modulation symbol setting method may be interchanged. In the case of the secondary cell, (NACK / NACK / DTX) and (DTX, NACK / DTX) can be considered to be integrated (NACK / DTX, NACK / DTX) in the converted HARQ-ACK state.

The following table is an example of a HARQ-ACK multiplexing transmission method for an M_P cell = 4 and an M_S cell = 5. For M = 5, the sixth example above is for cases where both S1 and S2 are DTX.

[Table 13]

2) HARQ-ACK bundling scheme

Alternatively, HARQ-ACK bundling may be used to consider setting the maximum value of M to four. Accordingly, the HARQ-ACK can be transmitted in the same manner as the PUCCH format 1b that can select a channel of the existing 3GPP LTE Rel-11 system. The application of the HARQ-ACK bundling scheme can be applied to a case where the number M of downlink (DL) subframes related to an uplink (UL) subframe to which a PUCCH is transmitted exceeds 4. As a more specific example, when scheduling the physical channels requiring HARQ-ACK to the UE for M = j (j> 4), the number of scheduled channels (or PDSCH transmission or downlink SPS release) PDCCH / EPDCCH) is greater than 4, the HARQ-ACK may be applied to HARQ-ACK bundling. In the embodiment of the present invention, the PDCCH / EPDCCH indicating the k-th scheduled PDSCH transmission or the downlink SPS release and the subframe including the PDCCH / EPDCCH are referred to as raw DAI. The HARQ-ACK bundling may be performed for HARQ-ACK for physical channels corresponding to a raw DAI exceeding 4 and HARQ-ACK for a physical channel corresponding to raw DAI = 4 (or DAI). As a specific example, when the number of channels to be scheduled is 5, the HARQ-ACK for the fifth channel (hereinafter referred to as a channel corresponding to raw DAI = 5) corresponds to the HARQ-ACK corresponding to the raw DAI = 4, Bundling can be performed.

[Table 14]

The reasons for considering ACK or DTX only for raw DAI = 4 above are as follows. In the existing table for PUCCH format 1b in which channel selection is possible, the state of (ACK, DTX, DTX, DTX) When the HARQ-ACK is NACK / DTX, the HARQ-ACK is not distinguished separately. In the above table, the HARQ-ACK for raw DAI = 5 can be said to have performed HARQ-ACK bundling for all HARQ-ACKs whose raw DAI value exceeds 4 when the number of scheduled channels is 6 or more. The additional HARQ-ACK bundling basically follows an AND operation, and when DTX is included, it can be limited to following Table 14 again.

In case of DTX for HARQ-ACK for raw DAI = 5, eNodeB may not actually perform scheduling, or it may have occurred due to PDCCH loss at the UE end although scheduling has been performed. In this case, HARQ-ACK may not be correctly represented for raw DAI = 4 when NACK processing is performed for (ACK, DTX) as shown in Table 13 above. Therefore, if the physical channel corresponding to the raw DAI = 4 (or DAI = 4, HARQ-ACK (3)) is the latest (last) subframe among the downlink (DL) subframes related to the uplink (UL) And may not perform the HARQ-ACK bundling when it is transmitted in a DL subframe. That is, in this case, there is no possibility that the PDCCH with the raw DAI = 5 is transmitted, and the UE does not lose the PDCCH, so there is no reason to perform the HARQ-ACK bundling. That is, if HARQ-ACK (HARQ-ACK (3)) for DAI = 4 is ACK in raw M = 5, ACK is processed and if NACK is NACK, eNodeB is processed as raw In the case of scheduling only DAI = 4, it is necessary to schedule DAI = 4 in the last subframe (the fifth subframe in case of M = 5 and the sixth subframe in case of M = 6) Can be prevented from being processed by the NACK. That is, in this case, HARQ-ACK (3) and HARQ-ACK (4) are not bundled even when HARQ-ACK (4) is set to DTX. In this embodiment, the contents of raw DAI = 4 and raw DAI = 5 or 6 are merely one example. The M value (4 in the embodiment) to be used for PUCCH format 1b transmission capable of channel selection and the channels (5 in the embodiment) of the maximum number of scheduling numbers of the mobile stations.

For the sake of convenience, it has been described that the downlink control information (DCI) is transmitted on the PDCCH. However, the present invention is not limited to this, and it is also possible to transmit on the other control channel such as EPDCCH. If the DAI field is limited to 2 bits, a value of 5 or more can not be directly indicated, and for example, a value of a field equal to DAI = 1 may be used. A value of Raw DAI = 5 or more is indirectly recognized through a history of DAI values in a previous PDCCH transmitted in a downlink (DL) subframe related to an uplink (UL) subframe to transmit PUCCH.

(3) How to configure HARQ-ACK bit when transmitting in PUCCH format 3

In PUCCH format 3, the number of input bits for HARQ-ACK is set to a maximum of 20 bits. The increase of the total number of HARQ-ACK bits due to the use of the remaining DL subframe of the FDD cell at the time of TDD-FDD carrier aggregation (CA) may be supported by utilizing additional HARQ-ACK bundling. The HARQ-ACK bundling may be performed on a cell-by-cell basis. Also, the HARQ-ACK bundling may be time domain bundling. Again, the time domain bundling scheme may utilize successive ACK counters.

(DL) subframe (hereinafter referred to as an FDD residual DL subframe) of an FDD cell arranged in an uplink (UL) subframe in a TDD cell and transmits a downlink (DL) subframe, and performs bundling according to the value of M. For consecutive ACK counters, when M = 3, 4, it can be expressed according to the following table. When the value of M is 5 or more, a method of performing bundling using the table corresponding to M = 4 from MSB to 4 bits and not bundling the remaining bits can be considered. Alternatively, instead of compressing to the last 2 bits per cell, we may consider reducing the number of bits in a manner that expands in the same way as M = 3 to represent ACK, ACK, ..., NACK / DTX, any. More specifically, the size of bundled bits per cell is designed not to exceed 4. Table 17 below is an example of a design for M = 5. The remaining states in Table 17 below can be used to further distinguish and distinguish HARQ-ACK combinations. In this case, the DAI value can be set for all downlink (DL) subframes arranged in a UL (UL) subframe for each cell.

In another method, DL subframes arranged in an uplink (UL) subframe in a TDD cell are divided into two groups, M values are designated for each group, and bundling is performed in a time domain. The two DL subframe groups may be limited to the presence or absence of an FDD residual DL subframe. For example, the total number of DL subframes associated with the uplink (UL) subframe excluding the DL subframe of the FDD cell (hereinafter referred to as FDD residual DL subframe) And performs bundling according to the value of M_1. For the FDD residual DL subframe, the M_2 value is set as the total number of FDD residual DL subframes associated with the UL subframe, and bundling is performed according to the M_2 value. In this case, the DAI value is set for FDD residual DL subframes and remaining DL subframes for a DL subframe arranged in an UL subframe for each cell. Can be separately set. That is, in this case, it is possible to have two kinds of DAI values for each uplink (UL) subframe.

Table 15 below shows consecutive ACK counters for M = 3.

[Table 15]

Table 16 below shows consecutive ACK counters for M = 4.

[Table 16]

Table 17 below shows consecutive ACK counters for M = 5.

[Table 17]

The following is a more specific example of when the bundling is applied.

As a first example, when the number of bits of the HARQ-ACK to be transmitted exceeds 20, time domain bundling is performed for each cell.

As a second example, when a UE capable of TDD-FDD carrier aggregation (CA) sets both TDD cells and FDD cells, time domain bundling is performed for each cell.

As a third example, we set whether to bundle with time domain through upper layer signal. In a case where the number of HARQ-ACK bits exceeds 20 without establishing time domain bundling more specifically, a part of the remaining DL subframe of the FDD cell may not be used.

The following is a specific example of the application method of the bundling according to the application timing.

As a first example, the time domain bundling is performed for each cell for every cell under the condition that time domain bundling is performed.

As a second example, in the condition that time domain bundling is performed, the time domain bundling is performed for each cell except for the primary cell.

As a third example, the time domain bundling is performed for each cell for each cell under the condition that time domain bundling is performed. Here, some cells may be FDD cells or cells including FDD residual downlink (DL) subframes.

(4) Introduced new PUCCH format

Unlike the existing 3GPP LTE Rel-11 system, in the TDD-FDD carrier aggregation (CA) situation, it is more frequent that the PUCCH format 3 does not support 5 cells. Accordingly, the number of cells subject to the maximum carrier aggregation (CA) may eventually degrade the flexibility of the network, and a new PUCCH format may be considered as a solution to the problem. As a more specific example, a new PUCCH resource can be allocated based on the type of PUSCH occupying 1 RB for each slot. This may be applied only to TDD-FDD carrier aggregation (CA), or may be applied only when there is an upper layer signal.

Alternatively, it may be considered to transmit using a plurality of PUCCH resources. At this time, HARQ-ACK for a DL sub-frame excluding a FDD residual DL sub-frame is transmitted through a first PUCCH resource, and an FDD residual DL is transmitted through a second PUCCH resource. And transmit the HARQ-ACK for the subframe. The additional PUCCH resource may be set in an upper layer or expressed as a function for a first PUCCH resource.

(5) PUSCH piggyback

As described above, the bundling method or the number of HARQ-ACK bits may vary depending on whether the PUCCH format 1b or the PUCCH format 3 is used when the HARQ-ACK is transmitted on the PUCCH. It is possible to consider a situation where the HARQ-ACK is piggybacked to the PUSCH and transmitted such that the PUCCH and the PUSCH are not simultaneously transmitted. The HARQ-ACK may be configured to disband bundling when transmitting HARQ-ACK to the PUSCH even in the case of bundling at the time of transmission to the PUCCH. Here, disassembling means that the bundle is returned to the state before the bundling is performed. Again, spatial bundling may be excluded from bundling, which is the object of disassembly, and bundling disassembly may be limited to setting through UL grant. For example, it is possible to set whether to disassemble the bundle for HARQ-ACK to be transmitted on the PUSCH according to the UL DAI value. In this case, the maximum number of aggregated cells may be limited. More specifically, in the case where the maximum number of aggregated cells is not limited, bundling corresponding to raw DAI> 4 may also be excluded in the bundling to be disassembled.

As another approach, HARQ-ACK to be transmitted to the PUSCH can be considered to borrow the HARQ-ACK to be transmitted on the PUCCH regardless of the channel selection PUCCH format 1b or the PUCHC format 3. [ That is, it can be interpreted that the bundling schemes applied to the transmission on the PUCCH are considered when transmitting on the PUSCH.

IV. Supporting Cross-Carrier Scheduling

It is possible to consider introducing cross-carrier scheduling between cells constituting a carrier aggregation (CA) for a UE performing a TDD-FDD carrier aggregation (CA). This can be applied only when the relationship between the cell performing the scheduling and the cell receiving the scheduling is of the same frame structure type. That is, the FDD cell can be scheduled only to the FDD cell, and the TDD cell can be considered to be scheduled only to the TDD cell. Considering uplink (UL) HARQ timing, it may be effective to apply cross-carrier scheduling only between cells having the same frame structure type as in the above scheme. In the case of downlink (DL) HARQ timing, the DL subframe can be used as much as possible by utilizing the HARQ timing scheduled by the FDD cell itself. On the other hand, when the TDD cell is the primary cell, different TDD setting schemes can be utilized. If the FDD cell is the primary cell, some loss of the DL subframe may occur depending on the setting combination. Alternatively, in introducing cross-carrier scheduling in a TDD-FDD carrier aggregation (CA), it may be provided only when the frame structure type for the scheduling cell is FDD. An advantage of this is that the restriction by the scheduling cell can be avoided in the FDD in which the downlink (DL) and uplink (UL) are always available.

V. Method to limit HARQ timing

As described above, when a new HARQ-ACK timing is designated to support HARQ-ACK feedback for a downlink (DL) subframe of all FDD secondary cells according to the UL-DL setting when the TDD cell is a primary cell, Can be increased.

Therefore, the present invention proposes a scheme of applying only some HARQ timing of Table 5 to all TDD primary cell UL-DL settings. Specifically, the timing defined in an arbitrary scheme in UL-DL setting 1 of Table 5 is a HARQ-ACK payload through 4 subframes for UL-DL setting of 10 ms period and UL-DL setting of 5 ms period, Dispersion can be distributed over two subframes for UL-DL setting of 5 ms period and UL-DL setting of 10 ms period in the arbitrary method and UL-DL setting 4 in the UL-DL setting 2 . For example, HARQ timing can be defined as shown in the following table.

[Table 18]

The embodiments of the present invention described above can be implemented by various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. More specifically, it will be described with reference to the drawings.

13 is a block diagram illustrating a wireless communication system in which the present disclosure is implemented.

The base station 200 includes a processor 201, a memory 202 and an RF unit (radio frequency (RF) unit 203). The memory 202 is connected to the processor 201 and stores various information for driving the processor 201. [ The RF unit 203 is connected to the processor 201 to transmit and / or receive a radio signal. The processor 201 implements the proposed functions, procedures and / or methods. In the above-described embodiment, the operation of the base station can be implemented by the processor 201. [

The UE 100 includes a processor 101, a memory 102, and an RF unit 103. [ The memory 102 is connected to the processor 101 and stores various information for driving the processor 101. [ The RF unit 103 is connected to the processor 101 to transmit and / or receive a radio signal. The processor 101 implements the proposed functions, procedures and / or methods.

The processor may comprise an application-specific integrated circuit (ASIC), other chipset, logic circuitry and / or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit may include a baseband circuit for processing the radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module is stored in memory and can be executed by the processor. The memory may be internal or external to the processor and may be coupled to the processor by any of a variety of well known means.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

Claims (10)

CLAIMS What is claimed is: 1. A method for performing HARQ operations at a user equipment (UE)
Wherein at least one TDD based cell and at least one FDD based cell are established according to a carrier aggregation (CA) and a specific TDD based cell is set as a primary cell of the carrier aggregation (CA) If the at least one FDD-based cell is set as a cell, the UE receives downlink data from each cell;
Confirming a Physical Uplink Control Channel (PUCCH) format to be used by the UE in order to transmit HARQ ACK / NACK for the downlink data;
Determining the number of transmission bits of the HARQ ACK / NACK if the UE is determined to use a particular PUCCH format for transmission of the HARQ ACK / NACK,
Wherein the maximum number of cells included in the carrier aggregation is limited so that the number of transmission bits of the determined HARQ ACK / NACK does not exceed the maximum number of bits allowed in the PUCCH format. Way. The method according to claim 1,
If the PUCCH format to be used is PUCCH format 3 and the maximum allowable bit is 20 bits,
Wherein the maximum number of cells included in the carrier aggregation (CA) is limited. The method according to claim 1,
If the PUCCH format to be used is PUCCH format 3, the maximum allowable bit is 20 bits, and the UL-DL setting of a specific TDD based cell corresponding to the primary cell corresponds to 2, 3, 4, or 5 If so,
Wherein the maximum number of cells included in the carrier aggregation (CA) is limited. The method according to claim 1,
And receiving a setting for the PUCCH format to be used through the RRC signal. The method according to claim 1,
Wherein the carrier aggregation includes at least one TDD-based premise cell, at least one FDD-based secondary cell, and at least one secondary cell based on TDD. A method for receiving HARQ ACK / NACK in a TDD-based cell,
A TDD-based cell includes a carrier aggregation (CA) as a primary cell, a TDD-based cell and an FDD-based cell as secondary cells;
Wherein the TDD-based cell corresponding to the primary cell determines a Physical Uplink Control Channel (PUCCH) format to be used by the user equipment (UE);
A TDD-based cell corresponding to the primary cell transmits downlink data to the UE;
And receiving HARQ ACK / NACK for the downlink data from the UE,
Wherein the maximum number of cells included in the carrier aggregation is limited so that the number of received bits of the HARQ ACK / NACK does not exceed the maximum number of bits allowed in the PUCCH format. NACK receiving method. The method according to claim 6,
If the PUCCH format to be used is PUCCH format 3 and the maximum allowable bit is 20 bits,
Wherein the maximum number of cells included in the carrier aggregation (CA) is limited. The method according to claim 6,
If the PUCCH format to be used is PUCCH format 3, the maximum allowable bit is 20 bits, and the UL-DL setting of a specific TDD based cell corresponding to the primary cell corresponds to 2, 3, 4, or 5 If so,
Wherein the maximum number of cells included in the carrier aggregation (CA) is limited. The method according to claim 6,
And transmitting configuration information for the determined PUCCH format through an RRC signal. The method according to claim 6,
Wherein the carrier aggregation includes at least one TDD-based premise cell, at least one FDD-based secondary cell, and at least one secondary cell based on TDD.

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